`You can go to live in France, but you cannot become a Frenchman. You can go to live in Germany or Turkey or Japan, but you cannot become a German, a Turk, or a Japanese. But anyone, from any corner of the Earth, can come to live in America and become an American.”
-Ronald Wilson Reagan
That is a great quote.
I will however note, that he said 'become an American', not 'become a hyphenated American'.
People that come here and assimilate to American culture, become actual Americans, are generally welcome. People that come here and want to being their socialism or communism with them, not so much. People that put the nation they came from over the one they expect to adopt them (ilhan omar for example) not so much.
Those are the square pegs that the original poster of this screed on DU wants to fit through round holes. If they were coming here to actually assimilate, that DUmmy wouldn't have any interest in them what so ever, and may in fact even support marginalizing them, like dems have done with Americans formerly of cuba, who know the horrors of socialism/communism.